1. Field of the Invention
The present invention relates to a signal reading apparatus and a test apparatus. More particularly, the present invention relates to a signal reading apparatus that reads an output signal from a solid-state image sensing device and a test apparatus that tests the solid-state image sensing device.
2. Related Art
A CCD (Charge Coupled Device) transfers electric charges photoelectrically converted by a photo diode based on a clock signal input from a driver (hereinafter, referred to as a DR) to output the charges as an electrical signal. A signal reading apparatus respectively measures a reset division and a data division in the electrical signal output from the CCD, and reads a difference between the reset division and the data division as pixel data for the CCD. Then, a variable gain amplifier (hereinafter, referred to as a VGA) amplifies a signal level of pixel data, and an analog-digital converter (hereinafter, referred to as an ADC) converts the pixel data into a digital signal.
In recent years, there has been developed a CCD for extremely operating at high speed in order to take moving images with high picture quality. Therefore, since the signal reading apparatus must be speeded up, there has become a problem that extremely high-speed VGA and ADC are required.